The present invention relates to a structure of a sealing section which glues a counter substrate to an array substrate with a sealant so that they face each other and more specifically to a sealing structure adapted for a pixel-on-top type of active matrix liquid crystal display panel.
In recent years, the demand has increased for developing liquid crystal display panels with higher angular aperture. To meet high aperture requirements, an approach of arranging pixel electrodes on the top layer of an array substrate is adopted.
With such a pixel-on-top structure, the following problems are involved in the process of etching an ITO film to form pixel electrodes. That is, in order to form an ITO film on the top layer on the array substrate side, it is required to ensure the thickness of a second interlayer insulating film between the ITO film and underlying signal lines. To this end, the second interlayer insulating film uses a multilayered structure and its top layer is made of an organic material. Therefore, the etching of the ITO film is limited to wet etching. The reason is that dry etching fails to ensure sufficient selectivity to the organic insulating film in the etching process and the resist stripping process.
In general, for wet etching of the ITO film, use is made of a strong acid etching solution in which aqua regia, oxalic acid, HBr, Hl, or the like is diluted with water with or without the addition of iron chloride or copper chloride. These etching solutions have the property of etching Al which is generally used as a material of signal lines.
In FIG. 8, there is illustrated a fragmentary cross-section of a boundary area between the display area and the driver circuit area of an array substrate. In this figure, 64 denotes a gate oxide film, 67 a first interlayer insulating film, 69 the leading portion of a signal line, 70 an insulating film made of an inorganic material (the lower layer of a second interlayer insulating film), 71 an insulating film made of an organic material (the upper layer of the second interlayer insulating film), and 73 a pixel electrode made of ITO. The display area is to the left side of broken line B, while the driver circuit area is to the right of broken line C. The boundary between broken lines B and C serves as a seal area 81.
On the seal area 81 is placed a sealant that glues a counter substrate to the array substrate so that they face each other. To ensure good adhesion between the counter substrate and the array substrate, the organic insulating film 71 is removed from the seal area 81. Thus, as the interlayer insulating film only the inorganic insulating film 70 is left on the signal line leading wiring 69. As a result, in the presence of a defect, such as a pinhole, in the insulating film 70, Al forming the signal lines may corrode and lead to disconnection. Thus, the seal area 81 is a region where disconnection is easy to occur.
An object of the present invention is to provide a structure in which disconnection is difficult to occur in the leading portions of wirings that extend across the seal area in an active-matrix liquid crystal display panel using a pixel-on-top structure and having driver circuits integrally incorporated in.
The other object of the present invention is to provide a structure of seal area which permits the position of sealant to be stabilized.